The present invention relates to a digital ballistic computer for the fire guidance system for a tubular weapon.
In order to calculate the ballistic data, such as tangent elevation and lead of the tubular weapon or flight time of the projectile in dependence on the actual firing data, such as distance of the target, type of ammunition and environmental parameters, e.g. barometric pressure, air temperature, head wind velocity, etc., the manufacturer of ammunition prepares so-called firing tables for every type of ammunition which contain tangent elevation, flight time and lead for discrete distances under fixed environmental conditions or environmental parameters. These environmental conditions correspond, for example, to the ICAO [International Civil Aviation Organization] atmosphere and are the so-called standard conditions. Environmental parameters deviating from the standard conditions are considered to be mutually independent and are listed in the firing tables as correction values.
Known ballistic computers calculate the ballistic data by reproducing, as accurately as possible, continuous functions which approximate firing table data under standard conditions in that these functions either form the basis of the circuit design in analog computers or the basis of the realized program in digital computers, the latter case involving the programming of formulas for the calculation of tangent elevation, lead and flight time in hardware and software. The structure of these functions approximating the firing table data is applicable to all types of ammunition, while coefficients contained in the functions are applicable, on the one hand, only for one type of ammunition and, on the other hand, must be varied according to the correction values if there are environmental parameters which deviate from the standard conditions.
The use of a single structure of the functions for all types of ammunition is a drawback inasmuch as it is impossible to approximate with sufficient accuracy all firing tables applicable for different types of ammunition in a single structure. The result is that, on the one hand, the calculated ballistic data are of different accuracy for different types of ammunition and, on the other hand, the tubular weapon can be retrofitted for a new type of ammunition only if the existing function structure is able to also approximate with sufficient accuracy the firing tables for the new type of ammunition without additional coefficients, which is possible only in the rarest of cases.
Moreover, the problem often arises that the firing tables produced for the first ammunition are changed in the course of time, with respect to number and type as well as value of the firing table parameters. Such changes can be made in the ballistic computer only with considerable changes in hardware and software.
A further drawback in the known ballistic computers is the convergence behavior of the approximation procedures. This behavior depends on the selected structure of the functions and on additionally required approximation parameters, such as, for example, the starting values. Since the optimizing problems are often nonlinear, it is very time consuming to find a satisfactory solution.